1. Field of Invention
The present invention relates to an electrode material, and more particularly to a plastics electrode material containing conductive polymers and having properties of fast charging and discharging and high capacity.
2. Description of the Related Art
Proton (hydrogen ion) secondary cell containing conductive polymers is a new type product after lithium secondary cell. Because proton has a smaller ion radius and faster ion speed, proton secondary cell has advantages of high working voltage, stable discharge curve, small self-discharge, long cyclic life and no pollution. Additionally, proton secondary cell can be totally made of polymers and provides a function of high current (10 amp for one cell) charging and discharging. Proton secondary cell can be applied to portable batteries (2 Ah), thin film batteries (200 μAh), small-sized batteries (200 mAh) and large-sized batteries (50 Ah).
Performance of proton secondary cell containing conductive polymers is highly related to properties of anode, cathode and electrolyte, especially anode. Furthermore, if anode material has higher potential than cathode material and good electron conduction property and change of the anode material composition does not greatly affect the cell voltage, the cell will have high working potential, plain curve of voltage, small IR resistance and low voltage drop. If anode material has reversibility on ion extraction/insertion, high diffusibility and storability and does not affect the cell volume with charging and discharging reaction, the cell will have high capacity, cycling life and stability. If anode material has high stability for the electrolyte and high thermal stability during charging, the cell will have cycling life and stability.
In other words, if a battery having good properties of high and stable working voltage, small IR resistance, low voltage drop, high capacity, cycling life and stability is prepared, the battery must use suitable anode material. Applying conductive polymers such as polyindole as anode and cathode materials under acidic conditions to proton secondary cell may have the advantages as follows: (1) the cell can be formed integrally on metallic foil, porous metallic substrate or conductive carbon substrate; (2) the cell has no memory effect and have a large number of charging and discharging cycles more than 100,000 times; (3) the cell can be manufactured with conventional processes; and (4) proton is a carrier for charging and discharging the cell.
Polyindole can be synthesized by electrochemical method or using oxidizing agents. The oxidizing agents comprise ferrous chloride and sodium thiosulfate. Because polyindole only contains hydrogen, nitrogen and carbon, polyindole is environmentally friendly. With advancing technology of manufacturing polyindole, polyindole is available commercially. Preformed polymer of cyclic polyindole tri-monomer is synthesized in prior art and has a capacity of 50 to 60 mAh/g with a charging and discharging mechanism of cation adsorption/desorption and a cyclic life of more 100,000 cycles at 90% charging and discharging. Thus, U.S. Pat. No. 6,300,015B1 Patent disclosed a cell having a separator between anode and cathode conductive polymers. However, the cell still has problems of low capacity and operating voltage compared to a lithium cell and is not suitable for practical applications.
Therefore, a main objective of the secondary cell industry is to increase anion absorption ability of anode material containing polyindole and conductivity of the cell so as to improve proton discharge efficiency of the cell.
To overcome the shortcomings, the present invention provides a plastics electrode material to mitigate or obviate the aforementioned problems.